FINE-NEEDLE ASPIRATION OF THYROID FOLLICULAR NEOPLASM - DIAGNOSTIC USE OF THYROID PEROXIDASE IMMUNOCYTOCHEMISTRY WITH MONOCLONAL-ANTIBODY-47

Background. We previously demonstrated that thyroid peroxidase (TPO) i mmunocytochemistry with monoclonal antibody 47 can help to differentia te benign (staining score, 80% or more) from malignant (staining score , less than 80%) thyroid nodules on fine-needle aspiration (FNA) sampl es. In the present study we assessed the use of TPO immunocytochemistr y in the cytologic diagnosis of thyroid follicular neoplasms. Methods. A total of 109 histologcally proven follicular tumors were studied. T here were 60 microfollicular adenomas, 23 atypical adenomas, 17 oncocy tic adenomas, and 9 follicular carcinomas. Adequate preoperative FNA s amples were available in all cases. TPO immunocytochemistry was perfor med on one half of the slides. Results. The staining score was less th an 80% in all follicular carcinomas, whereas it was 80% or more in 68 of 100 benign tumors. There was no false negative and 32 false positiv es for diagnosis of malignancy. The false positives were 10 microfolli cular adenomas, 13 atypical adenomas, and 9 oncocytic adenomas. TPO im munocytochemistry has a sensitivity of 100% and a specificity of 68%. Conclusions. TPO immunocytochemistry with monoclonal antibody 47 on FN A samples is a highly sensitive and fairly specific method to distingu ish benign from malignant follicular neoplasms. This technique can hel p to reduce the number of surgical procedures for benign thyroid nodul es without increased risk of overlooking malignancy.